Error concealment method and device

Abstract

The invention concerns a method of concealing errors in at least one part of a current image (i) a sequence of images ( 4 ), characterized in that it comprises the following steps: comparing (S 81 ) said at least one part of the current image (i) with at least one corresponding part of a previous image (i−1), and selecting (S 83 ) a temporal error concealment method or a spatial error concealment method to be applied in said at least one part of the current image, according to the result of said comparison step and at least one item of information relating to the errors concealed in said at least one corresponding part of the previous image.

What we claim is: 
     
       1. A method of concealing errors in at least part of a current image in a sequence of images, comprising the following steps of:
 comparing the at least one part of the current image with at least one corresponding part of a previous image; 
 determining a parameter representing a measurement of similarity between the at least one part of the current image and the at least one corresponding part of the previous image from the result of the comparison of the at least one part of the current image with the at least one corresponding part of the previous image; and 
 selecting a temporal error concealment method or a spatial error concealment method to be applied in the at least one part of the current image, according to the result of said comparing step and at least one item of information relating to the errors concealed in the at least one corresponding part of the previous image, 
 wherein said selecting step comprises a substep of comparing the parameter representing the measurement of similarity with a threshold determined from the at least one item of information relating to the errors concealed in the at least one corresponding part of the previous image; 
 the threshold represents a similarity value at which the at least one current image part and the at least one corresponding previous image part are no longer considered to be similar, and 
 the at least one item of information relating to the errors concealed and the threshold comprise an item of information representing an amount of concealed data in the at least one corresponding part of the previous image. 
 
     
     
       2. A method according to  claims 1 , wherein, when the amount of concealed data is zero for a predetermined number of consecutive previous images, the threshold is reset to a predetermined value. 
     
     
       3. A method according to  claim 1 , wherein, during said selecting step, a temporal error concealment method or a spatial error concealment method is selected according to the result of the comparison of the parameter representing a similarity measurement with the threshold. 
     
     
       4. A method according to  claim 1 , wherein said comparing step comprises the comparison of the value of at least some of the pixels of the at least one current image part with the value of at least some of the pixels of the at least one corresponding part of the previous image respectively. 
     
     
       5. A method according to  claim 1 , wherein the selection of the error concealment method to be applied in the at least one part of the current image is also made according to the type of coding of the at least one part of the current image. 
     
     
       6. A method according to  claim 1 , wherein the at least one item of information relating to the concealed errors comprises an item of information representing the concealment method applied in the at least one corresponding part of the previous image. 
     
     
       7. A method according to  claim 1 , wherein the previous image corresponds to the image decoded before the current image. 
     
     
       8. A method according to  claim 1 , wherein the previous image corresponds to the image preceding the current image in the order of display of the images in the sequence. 
     
     
       9. A method according to  claim 1 , wherein said comparing step comprises the comparison of a histogram of the current image with a histogram of the previous image. 
     
     
       10. A device for concealing errors in at least one part of a current image in a sequence of images, comprising:
 at least a processor and memory, cooperating to function as: 
 a comparison unit configured to compare the at least one part of the current image with at least one corresponding part of a previous image; 
 a determination unit configured to determine a parameter representing a measurement of similarity between the at least one part of the current image and the at least one corresponding part of the previous image from the result of the comparison of the at least one part of the current image with the at least one corresponding part of the previous image; and 
 a selection unit configured to select a temporal error concealment method or a spatial error concealment method to be applied in the at least one part of the current image according to the result obtained by said comparison unit and at least one item of information relating to the errors concealed in the at least one corresponding part of the previous image,. 
 wherein said selection unit compares the parameter representing the measurement of similarity with a threshold determined from the at least one item of information relating to the errors concealed in the at least one corresponding part of the previous image; 
 the threshold represents a similarity value at which the at least one current image part and the at least one corresponding previous image part are no longer considered to be similar, and 
 the at least one item of information relating to the errors concealed and the threshold comprise an item of information representing the amount of concealed data in the at least one corresponding part of the previous image. 
 
     
     
       11. A device according to  claim 10 , wherein said comparison unit compares the value of at least some of the pixels of the at least one part of the current image with a value of at least some of the pixels of the at least one corresponding part of the previous image respectively. 
     
     
       12. A device according to  claim 10 , wherein said comparison compares a histogram of the current image with a histogram of the previous image. 
     
     
       13. A non-transitory computer-readable storage medium storing an executable program for causing a computer to execute a method according to  claim 1 . 
     
     
       14. A storage medium according to  claim 13 , wherein said storage medium is partially or totally removable.